Identification of Actuation System and Aerodynamic Effects of Direct-Lift-Control Flaps

A maximum likelihood parameter estimation method for nonlinear systems has been applied to flight data of the research aircraft ATT AS (advanced technologies testing aircraft system). The emphasis is on modeling and identification of 1) dynamics and nonlinearities of actuation systems for the direct-lift-control (DLC) flaps, and 2) their aerodynamic effectiveness and other influences. These specially designed flaps provide an additional longitudinal control suitable for in-flight simulation or load alleviation investigations. The identification results indicate that under aerodynamic loads the possible maximum flap deflections are severely limited. The flightestimated aerodynamic characteristics are compared with those predicted by wind tunnel and analytical methods. It is found that the DLC flaps are somewhat less effective aerodynamically than they were designed for. More importantly, the transit time lag in the downwash generated due to flap deflections significantly affects the dynamic pitching motion. Furthermore, it leads to certain additional unsymmetrical and interference effects.

[1]  R. E. Maine,et al.  AGARD Flight Test Techniques Series. Volume 3. Identification of Dynamic Systems - Applications to Aircraft. Part 1. The Output Error Approach , 1986 .

[2]  R. E. Maine,et al.  MAXIMUM LIKELIHOOD ESTIMATION OF TRANSLATIONAL ACCELERATION DERIVATIVES FROM FLIGHT DATA , 1979 .

[3]  J. E. Murray,et al.  Flight testing a highly flexible aircraft - Case study on the MIT Light Eagle , 1990 .

[4]  R. V. Jategaonkar,et al.  Two complementary approaches to estimate downwash lag effects from flight data , 1991 .

[5]  K. W. Iliff,et al.  Parameter Estimation for Flight Vehicles , 1989 .

[6]  K.-U. Hahn,et al.  ATTAS - Recent Flying Qualities Experiments , 1991 .

[7]  R. V. Jategaonkar,et al.  Algorithms for aircraft parameter estimation accounting for process and measurement noise , 1989 .

[8]  K.-U. Hahn,et al.  Load Alleviation and Ride Smoothing Investigations Using ATTAS. , 1990 .

[9]  William R. Wells,et al.  The influence of unsteady aerodynamics on extracted aircraft parameters , 1979 .

[10]  R. Jategaonkar Determination of Aerodynamic Characteristics from ATTAS Flight Data Gathering for Ground Based Simulator , 1991 .

[11]  Vladislav Klein,et al.  Estimation of aircraft aerodynamic parameters from flight data , 1989 .

[12]  William R. Wells,et al.  Simplified Unsteady Aerodynamic Concepts with Application to Parameter Estimation , 1979 .

[13]  H. J. Smith,et al.  Flight-Determined Stability and Control Derivatives for an Executive Jet Transport , 1975 .